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Updated: Aug 19, 2026

Electrophysiological Motor Unit Number Estimation (MUNE) Measuring Compound Muscle Action Potential (CMAP) in Mouse Hindlimb Muscles
Published on: September 25, 2015
Competition for survival between motor units in mouse skeletal muscle
M D Habgood1, W G Hopkins, J R Slack
1Department of Physiology, University of Auckland, School of Medicine, New Zealand.
Abstract:
The soleus nerve on one side of neonatal mice was crushed and the soleus muscle on the same side was surgically reduced in size. Some animals also had their lumbar spinal nerve 5 (L5) cut and misdirected in the same operation. Three months later, the number of L5 and L6 soleus motor units in the operated muscles was counted electrophysiologically and the number of muscle fibers was counted histologically. The number of L6 motor units in reduced size muscles without L5 innervation was significantly greater than it was in muscles where both L5 and L6 motor units were present. This result supports the concept that motor neuron survival during development is dependent upon the number of muscle fibers available for innervation and the number of motor neurons competing to innervate them.
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